1. Field of the Invention
The present invention relates to a photo fixer and thermal printer having the same. More particularly, the present invention relates to a photo fixer and thermal printer having the same, in which a control of an amount of fixing rays can be efficient and easy, and no shutter for shielding fixing rays is required.
2. Description Related to the Prior Art
A color thermal printer is used with color thermosensitive recording paper, and produces full-color prints. The recording paper includes a support and at least three thermosensitive coloring layers overlaid thereon. Among the three, a coloring layer which is positioned the farther from the support has a higher heat sensitivity, and colorable in response to lower heat energy. The two coloring layer being not near to the support have such fixability that its coloring ability is destroyed when near ultraviolet or ultraviolet rays is applied to the recording paper. While the recording paper is moved back and forth in the color thermal printer, a thermal head pressurizes and heats the recording paper to record three color images to the coloring layers. After the thermal recording, a photo fixer is driven to apply ultraviolet rays to the recording paper. The first and second coloring layers are fixed and prevented from developing further color upon coloring of the second and third coloring layers.
The use of light sources including mercury has been recently reconsidered because waste mercury contaminates the environment. In view of this, JP-A 2001-155688 suggests the photo fixer which is constituted by a xenon lamp free from mercury. However, the xenon lamp is in a rod shape, is circular as viewed in cross section, and emits ultraviolet rays at a regular intensity in any of portions in the entirety of the xenon lamp. There is a suggestion of a reflector, which is disposed in the vicinity of the xenon lamp, and reflects waste part of the ultraviolet rays toward the recording paper with high performance of reflection.
When the xenon lamp of the straight shape is used, it is impossible to limit a ray applying region of ultraviolet rays without adding extra elements to the xenon lamp. So a shutter mechanism is additionally disposed in the color thermal printer for use with the recording paper of a continuous type. The shutter mechanism is set to cover an unrecorded portion in the recording paper when the photo fixer consists of the xenon lamp of the straight type. However, a problem arises in that the shutter mechanism has a considerable dimension and is inconsistent to reduction of the size of the color thermal printer.
In general, states of fixing the coloring layers are important for high quality in printing the image. The use of the xenon lamp has a shortcoming in much difficulty in controlling the light amount because efficiency in the light emission is heightened by application of high frequency between electrodes. It is very difficult to set the xenon lamp at a desired intensity of light. Thus, high quality in printing is hard to obtain due to a difference between the fixing states of the coloring layers.